-- There are systems for the directional detection of electrons known from the publication: W. Slówko, “Directional detection of secondary electrons for electron beam profilography”, Vacuum 52 (1999), page 441, and Polish patent descriptions: no. 1766333 entitled “Secondary electron detection unit”, no. 180420 entitled “System for signal processing in a scanning electron microscope”, no. P316499 entitled “Method of surface topography reconstruction in a scanning electron microscope”, and P363131 entitled “Electron detection system for a scanning electron microscope”. They consist of a symmetrical disposition of two or more electron detectors above the examined sample surface. Each of the detectors should collect electrons coming from another sector of the solid angle of the electron emission. That means that the electron detection occurs simultaneously in all the angle sectors. Signals obtained from particular detectors depend on the emission currents in the matching angle sectors and may be used for determining the local slope angles of the surface examined and for its three dimensional reconstruction. - -
-- There are solutions of electron detection systems known from the patent applications: no. P329339, entitled “High pressure scanning electron microscope”, and United States patent application publication US 2006/0027748 Al, entitled “Secondary electron detector system for a scanning electron microscope”, which are composed of a microporous plate, advantageously of the microsphere type, and a secondary electron detector of the scintillation type. In both solutions, the stream of secondary electrons, irrespectively of their emission directions, is brought into a hole in the lower wall of an intermediate chamber which is biased with a proper voltage. So the signal does depend substantially on the directions of the secondary electron emission that are detected. --
Then, the detection systems based on the known method of the directional electron detection are composed of two or more electron detectors disposed symmetrically around the axis of the electron beam scanning the examined sample surface, and a set of electrodes biased properly with constant voltages which should ensure a laminar flow of emitted electrons according to the directions of their emission. In case of the detection of backscattered electrons, the detector system may be relatively simple and composed of two or four semiconductor diodes of the p-i-n type connected with proper amplifiers for their signals. However, the detector system for secondary electrons is much more complex. It must contain two or four complete scintillator detectors of the Everhart-Thornley type, that is, a scintillator with its high voltage supply, a light pipe, a photomultiplier with its voltage supply and a signal amplifier for each of the two or four detector channels.